Special Charges (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	$ 882	$ 5,199	$ 874	$ 882	$ 1,309
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down				879
Total restructuring charges, net	$ 16,910	5,186	5,848	2,559
Inventories		137,309	143,682
Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down			921
Energy Segment
Restructuring Cost and Reserve [Line Items]
Total restructuring charges, net		(1,181)	3,661	54
Advanced Flow Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charges, net		$ 595	626	2,505
Corporate Segment [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charges, net				$ 13,096
Corporate Segment [Member] | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down			$ 0